PLA composites reinforced with rice residues or glass fiber—a review of mechanical properties, thermal properties, and biodegradation properties

Fiber reinforced polylactic acid (PLA) composites are one of the current research hotspots. Rice residues (RR) and glass fiber (GF) are commonly used as raw materials for strengthening PLA composites. In this paper, the mechanical properties, thermal properties and degradation properties of RR/PLA and GF/PLA composites were reviewed. The results showed that the defect in fiber (RR, GF) reinforced PLA is significantly improved by modification and the mechanical properties are improved by about 40%. The main reason is the unification of the surface polarity of fibers and PLA, as well as the role of connection established by the functional groups. Meanwhile, the surface modification of RR/PLA and GF/PLA composites can also improve their thermal and degradation properties. RR/PLA composites has worse heat resistance than pure PLA, whereas GF/PLA composites has better thermal stability than pure PLA. The crystallinity of RR/PLA composites was generally higher than that of pure PLA, indicating that natural fibers played the role of nucleating agent and promoted the nucleation of PLA. The pyrolysis loss of natural fiber reinforced PLA composites begins at 100 °C and can be divided into three stages: evaporation of water within the fiber, degradation of cellulose and hemicellulose, and degradation of non-fiber components. At about 300 °C, the degradation rate is the highest, and the weight loss ratio is above 90% at the end of the pyrolysis process. In terms of degradation performance, RR/PLA composites has excellent biodegradability, and its biodegradability increases with the increasement of RR content. Degradation of GF/PLA composites is only degradation of PLA, so the decline of mechanical properties of GF/PLA composites is weakened. It can be predicted that with the advent of the era of carbon neutrality, the green degradable PLA composite technology will be developed deeply and quickly.